The head of the London 2012 organising committee has voiced fears that with just 200 days to go until the opening ceremony from Monday, the "extraordinary opportunity" presented by the Games remains widely under-appreciated by the public.

Paul Deighton, chief executive of the London Organising Committee of the Olympic and Paralympic Games (Locog), said he was concerned that many businesses and members of the public would not recognise its scale until shortly before it started.

"When the world starts arriving here, the light will begin to go on and people will start to say 'Wow, I had no idea. This will be the experience of a lifetime.' This is my real concern," he said.

"The thing that keeps me up at night is whether we will take full advantage of the extraordinary opportunity coming our way this summer. I know that by the time we get to the end of this most people will say that they had no idea of the scale and opportunity of this, if only. I don't want too many if onlys."

Locog will formally take control of the Olympic Park in east London from the Olympic Delivery Authority that has spent £7.1bn of public money building the venues on it. This week, the prime minister will chair a special Olympics cabinet to discuss progress to date.

Deighton said parents in particular should "feel a responsibility to make sure their kids experience these Games in every way they possibly can, because they won't see this again in their lifetimes". All the permanent venues are now completed, but Deighton said there was still "a massive amount to do" in preparing the Olympic Park for the Games.

There are also important temporary venues to be built, for example in Greenwich Park for the equestrian events and on Horse Guards Parade for the beach volleyball. On the park itself, Locog must build temporary facilities for sponsors, merchandising outlets, cavernous catering facilities, a double-sided big screen that will float on a canal and provide a Henman Hill-style viewing area, broadcast facilities and cabling.

Technology and operations will be tested at two more clusters of preparatory events, starting this week at the O2 at Greenwich with a gymnastics event.

"Ninety-two percent of our time has elapsed but we have considerably more than 8% of the work left to do. And the work we have left to do will determine whether the Games are ultimately successful," Deighton told the Guardian.

"This is where it really counts. We have cleared away all the obstacles that would stop us delivering the inspiring Games we all want to have. Those big issues have been dealt with. Now we have to pay attention to the detail on multiple fronts."

Last week, the ticketing process came in for fresh criticism after Locog was forced to suspend the resale process for those who could no longer use their tickets after complaints about its website. The final batch of 1.3m tickets will go on sale in April. In all, 8.8m ticketholders will attend the Games.

"People probably don't understand how hard this is. It's massive. Any business is about having crystal clear clarity about what you're trying to do, having the resources to do it – those are the things we've put in place – and the final component is effective execution," said Deighton.

Locog has been praised for raising £700m in commercial revenue and the majority of its £650m ticket revenue target well ahead of the Games. But Deighton said that while London was in better shape at this stage than almost any other host city, the hardest part of the job was still to come.

"If you had said to me when I took this job in December 2005, would you take this position with 200 days to go, particularly if you explained the economic position the world would find itself in, I'd take it in a heartbeat. But that doesn't in any way diminish our understanding of the massive challenge in the last seven months of delivering an event of this incredible scale," he said.